1. Technical Field
The present invention relates to a method for manufacturing a semiconductor device, having a step of separating semiconductor device(s) formed over a base, from the base.
2. Related Art
Japanese Laid-Open Patent Publication No. 10-125929 describes a method of separation which includes a step of forming an object-to-be-separated over a transparent substrate, while placing a light absorption layer (amorphous silicon layer, for example) in between, and a step of irradiating a laser light from the back side of the substrate over the entire region right under the object-to-be-separated. Japanese Laid-Open Patent Publication No. 10-125929 describes that the object-to-be-separated may be separated from the substrate, because the laser irradiation induces a phase change in the light absorption layer.
Japanese Laid-Open Patent Publication No. 2007-35825 describes a method for manufacturing a semiconductor device, providing a heat-decomposable removal layer between a support substrate and a seed metal layer of a semiconductor device, and heating and decomposing the removal layer to thereby separate the seed metal layer of the semiconductor device from the support substrate. Japanese Laid-Open Patent Publication No. 2007-35825 describes that only the removal layer may be heated using a certain wavelength of laser light capable of transmitting through the support substrate but incapable of transmitting through the removal layer.
There are, however, some room for improvement in the conventional techniques described in these literatures, in the following aspects.
The technique of Japanese Laid-Open Patent Publication No. 10-125929 has been anticipated for damages possibly given to the object-to-be-separated, because the laser is irradiated over the entire region right under the object-to-be-separated. The technique of Japanese Laid-Open Patent Publication No. 10-125929 also adopts an intermediate layer including a metal reflective layer, provided over the light absorption layer, so as to suppress the laser transmission and thereby suppress the damage. Addition of this sort of component, however, complicates the process and increases the cost of manufacturing.
Another problem is that the irradiation over the entire region right under the object-to-be-separated using the laser having only a very small beam spot worsens the throughput, remained for further improvement.
The technique of Japanese Laid-Open Patent Publication No. 2007-35825 has a room for improvement in the aspects below.
First, when the laser was directly irradiated to a semiconductor chip contained in the semiconductor device, polyimide used for an interlayer insulator between interconnects, or to the removal layer right under the via plug, these components may be adversely affected by abrasion or generated heat. In particular, the via plug formed so as to penetrate the interconnect layer has a large heat conductivity. The heat may, therefore, conduct therethrough to reach an encapsulation resin, to thereby degrade the reliability of a package.
Second, irradiation of laser having a very small beam spot over the entire surface of the support substrate has been worsening a throughput, and has been remained for further improvement.